U.S. patent application number 12/545491 was filed with the patent office on 2009-12-17 for communication resource management device.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Atsushi Shinozaki.
Application Number | 20090310557 12/545491 |
Document ID | / |
Family ID | 32750590 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090310557 |
Kind Code |
A1 |
Shinozaki; Atsushi |
December 17, 2009 |
COMMUNICATION RESOURCE MANAGEMENT DEVICE
Abstract
A communication resource management device is capable of
changing the transfer rate of a control channel related to a mobile
terminal in accordance with the communication condition. The device
determines whether to change the transfer rate of a first control
channel related to a first mobile terminal; determines whether
there is a frequency band for which it is not determined whether
the frequency band is to be used in a predetermined time period
based on the current transfer rate of a second control channel
related to a second mobile terminal and an amount of data of
signals to be transmitted in the second control channel; and
allocates, to the first mobile terminal, at least a part of the
frequency band for the second control channel with respect to the
second mobile terminal in a predetermined period of time based on a
positive decision result. The device changes the transfer rate in
the first control channel while maintaining the total frequency
band for plural control channels related to plural mobile terminals
at a constant value.
Inventors: |
Shinozaki; Atsushi;
(Kawasaki-shi, JP) |
Correspondence
Address: |
KATTEN MUCHIN ROSENMAN LLP
575 MADISON AVENUE
NEW YORK
NY
10022-2585
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
32750590 |
Appl. No.: |
12/545491 |
Filed: |
August 21, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11063465 |
Feb 23, 2005 |
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12545491 |
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PCT/JP2003/000602 |
Jan 23, 2003 |
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11063465 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 28/20 20130101;
H04W 92/12 20130101; H04W 36/16 20130101; H04W 28/12 20130101; H04W
28/22 20130101; H04W 76/20 20180201; H04W 88/12 20130101; H04W
28/06 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/00 20090101
H04W072/00 |
Claims
1. A communication resource management device managing transmission
bands for a plurality of control channels concerning a plurality of
mobile terminals, comprising: an allocation part configured to
apply a first control channel of the plurality of control channels,
which first control channel is transmitted according to a
predetermined period, for transmitting a control signal for a
second mobile terminal of the plurality of mobile terminals,
unilaterally without any signal transmission with the second mobile
terminal although the first control channel has not been used for
transmitting the control signal for the second mobile terminal the
last time, when using the first control channel for transmitting
the control signal for the second mobile terminal, which first
control channel has been used for transmitting a control signal for
a first mobile terminal of the plurality of mobile terminals at
timing, at subsequent timing according to the predetermined
period.
2. A method for allocating a control channel in a mobile
communication system having a communication resource managing
device managing transmission bands for a plurality of control
channels concerning a plurality of mobile terminals, the method
comprising: applying a first control channel of the plurality of
control channels, which first control channel is transmitted
according to a predetermined period, for transmitting a control
signal for a second mobile terminal of the plurality of mobile
terminals, unilaterally without any signal transmission with the
second mobile terminal although the first control channel has not
been used for transmitting the control signal for the second mobile
terminal the last time, when using the first control channel for
transmitting the control signal for the second mobile terminal,
which first control channel has been used for transmitting a
control signal for a first mobile terminal of the plurality of
mobile terminals at timing, at subsequent timing according to the
predetermined period.
3. A mobile terminal of a plurality of mobile terminals used in a
mobile communication system having a communication resource
managing device managing transmission bands for a plurality of
control channels concerning the plurality of mobile terminals, the
mobile terminal comprising: a receiving part configured to receive
a control signal, which is transmitted by using a first control
channel of the plurality of control channels without any signal
transmission with the mobile terminal although the first control
channel has not been used for transmitting the control signal for
the mobile terminal the last time, which first control channel is
transmitted according to a predetermined period, when the first
control channel is used for transmitting the control signal for the
mobile terminal, which first control channel has been used for
transmitting a control signal for another mobile terminal of the
plurality of mobile terminals at timing, at subsequent timing
according to the predetermined period."
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to devices for
managing communication resources, and more particularly, to a
communication resource management device for varying the transfer
rate of a control channel.
[0003] 2. Description of the Related Art
[0004] A user of a mobile terminal in a mobile communication system
can communicate with a desired party by using a communication
channel (or information channel) that is set for each call. Setting
and management of the communication channel are performed via a
control channel. In this case, the data transfer capacity required
for the control channel generally differs for each communication
system or network. Thus, in terms of effective use of communication
resources, it is preferred that allocation of communication
resources for the control channel be modified for each
communication system.
[0005] In regard to this point, Japanese Patent No. 3282708
discloses a technique for improving the efficiency in using
communication resources by setting, for each network, an
appropriate quantitative ratio on a time axis of the control
channel to the information channel. A wireless terminal in this
case can establish a connection to any network having a different
channel structure by appropriately selecting an operational mode
corresponding to each network. However, even within the same mobile
communication system, the transfer capacity and/or traffic volume
required for the control channel are not always the same. For
example, generally, the number of control steps and the transfer
quantity of control information are large at the time of connecting
a call, but they are reduced during the connection. Thus,
conventional techniques such as mentioned above include problems in
that it is impossible to flexibly handle such a communication
condition.
[0006] On the other hand, in a CDMA (Code Division Multiple Access)
communication system based on the specification of the 3GPP (3rd
Generation Partnership Project), a predetermined transmission band
(transfer rate) is assigned for each control channel, and a fixed
transfer rate in the control channel is guaranteed in each network.
When improving the transfer rate in the control channel related to
a certain mobile terminal, a further transmission band is allocated
to the mobile terminal without modifying the allocation of
transmission band with respect to the control channels of other
mobile terminals. Thereby, the data amount that can be transferred
within a given length of time is increased in the control channel,
and it becomes possible to improve the communication speed. A
description of such a condition is given with reference to FIG.
1.
[0007] As shown in the left side of FIG. 1, among the available
transmission bands in an entire mobile communication system, a part
thereof is used for control channels (102), another part thereof is
used for a communication channel (104), and the remaining part is
empty transmission bands (106). For example, it is assumed that, in
order to guarantee a fixed transfer rate with respect to N mobile
terminals, a Tw transmission band is allocated to the control
channel for each of the mobile terminals, and N.times.Tw
transmission band resources are used for the control channels (102)
in the entire system. If two (2.times.Tw) transmission bands are
allocated to a certain mobile terminal in order to improve the
transfer rate of the control channel for the mobile terminal, as
shown in the right side of FIG. 1, the transmission bands used for
the control channels are (N+1).times.Tw in the entire system. Since
the mobile terminal can use 2.times.Tw transmission bands, it
becomes possible to improve the transfer rate in the control
channel.
[0008] However, when the transfer rate is improved in the
aforementioned manner, since the transmission bands allocated in a
fixed manner are increased among the available transmission bands
in the entire system, a problem occurs in that the unused bands 106
are reduced. It should be noted that the communication channels 102
include fixed transmission bands necessary for providing various
services offered in the mobile communication system, such as an
audio channel.
[0009] When the unused bands 106 are reduced, first, the number of
users that can be further handled in the system is decreased. In
addition, since the empty transmission bands vary in accordance
with variation in the transmission bands occupied by the control
channels, it becomes necessary to perform transmission band
management including, for example, monitoring of the empty
transmission bands. Consequently, there is a problem in that, for
example, management costs in a wireless base station and a radio
network controller (RNC) are increased. Further, since it is
necessary to, for example, design a system and conduct business
investment in consideration of the above-mentioned aspects, there
is a problem in that system building is not necessarily easy.
SUMMARY OF THE INVENTION
[0010] A general object of the present invention is to provide an
improved and useful communication resource management device in
which one or more of the above-mentioned problems are
eliminated.
[0011] Another and more specific object of the present invention is
to provide a communication resource management device capable of
effectively using communication resources by varying the transfer
rate of a control channel associated with a mobile terminal in
accordance with the communication state.
[0012] A further object of the present invention is to provide a
communication resource management device capable of varying the
transfer rate in a communication channel associated with a mobile
terminal without modifying the sum of the respective transmission
bands of communication channels allocated to plural mobile
terminals.
[0013] The above-mentioned objects are achieved by the means
mentioned below. According to the present invention, there is
provided a communication resource management device managing
transmission bands for a plurality of control channels related to a
plurality of mobile terminals including at least first and second
mobile terminals, the communication resource management device
including: first determination means for determining whether to
change a transfer rate of a first control channel related to the
first mobile terminal; and allocation means for allocating, to the
first mobile terminal, a transmission band for a second control
channel with respect to the second mobile terminal in a period of
time based on a decision result of the first determination means,
the decision result indicating change should be made.
[0014] Other objects, features and advantages of the present
invention will become more apparent from the following detailed
description when read in conjunction with the following
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic diagram showing a breakdown of
transmission bands that can be used in a mobile communication
system;
[0016] FIG. 2 is a schematic diagram of a mobile communication
system to which the present invention may be applied;
[0017] FIG. 3 is a block diagram of major functions of a
communication resource management device according to an embodiment
of the present invention;
[0018] FIG. 4 is a schematic diagram showing a breakdown of
transmission bands that can be used in the mobile communication
system;
[0019] FIG. 5 is a diagram for explaining how transmission blocks
to be transferred in respective control channels are transferred on
a time axis;
[0020] FIG. 6 is another diagram for explaining how transmission
blocks to be transferred in respective control channels are
transferred on a time axis;
[0021] FIG. 7 is a timing chart showing relationships among a
transfer rate, a transmission time interval (TTI), and a
transmission signal size (TFS);
[0022] FIG. 8 is a data diagram showing a general signal
format;
[0023] FIG. 9 is a timing diagram showing signal transfer in
downlinks according to a second embodiment; and
[0024] FIG. 10 is a timing diagram showing signal transfer in
uplinks according to the second embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0025] FIG. 2 is a schematic diagram of a mobile communication
system 200 to which the present invention may be applied. The
mobile communication system 200 is, for example, a CDMA
communication system based on the specification of the 3GPP. The
mobile communication system 200 includes a network 202 such as the
Internet, and the network 202 is provided with switching equipment
201 for establishing a connection with another communication system
such as a fixed telephone network. The mobile communication system
200 includes radio network controllers (RNCs) 204 connected to the
network 202. Each radio network controller 204 controls plural
wireless base stations 206 connected thereto. Each of the wireless
base stations 206 performs radio communications with a mobile
terminal 208 that belongs to its own region (cell). Allocation of
communication resources such as the transmission bands (transfer
rates) for mobile phones is managed by the radio network controller
204. In FIG. 2, Iu indicates the interface between the switching
equipment 201 in the network 202 and the radio network controllers
204. Iub indicates the interface between the radio network
controllers 204 and the wireless base stations 206. Uu indicates
the interface between the wireless base stations 206 and mobile
terminals 208.
[0026] FIG. 3 is a block diagram regarding major functions of a
communication resource management device according to one
embodiment of the present invention. For convenience of
explanation, the communication resource management device 300 of
this embodiment is provided in the radio network controller 204.
However, this is not fundamental to the present invention, and the
communication resource management device 300 may be provided
separately from the radio network controller 204. It should be
noted that FIG. 3 shows major blocks related to control channels,
which are particularly important in the present invention, and
those blocks related to processing of communication channels are
omitted.
[0027] The communication resource management device 300 includes
first interfacing means 302 for communications with the higher
switching equipment 201, and second interfacing means 304 for
communications with the lower wireless base stations 206. The first
and second interfacing means 302 and 304 include switching means
306 for appropriately delivering signals in the communication
resource management device 300. The communication resource
management device 300 includes transmission/reception process means
308, control signal processing means 310, and transmission band
management means 312, which are coupled to the switching means
306.
[0028] The transmission/reception process means 308 include
combining means 314 for receiving control signals (signals
transferred in control channels) from respective mobile terminals
via the first or second interfacing means 302 or 304, respectively,
and the switching means 306 as plural sequences of signals, and
converting them into a single signal sequence. The output of the
combining means 314 is connected to the switching means 306. The
transmission/reception process means 308 include allocation means
316 for determining how to transfer a control signal for each
mobile terminal to a wireless base station, and dividing means 318
for dividing an output signal of the allocation means 316 into
plural signal sequences for transferring.
[0029] The allocation means 316 include conversion means 320 for
converting the format of a control signal to be transferred to a
mobile terminal to a signal format for the Iub from the signal
format for delivering within the communication resource management
device 300. The output of the conversion means 320 is connected to
transmission time interval/size adjusting means 322 for adjusting
the transmission time interval (TTI) of a signal or the size of
data to be transferred at a time at each transmission cycle (TFS:
Transport Format Set). The output of the transmission time
interval/size adjusting means 322 is connected to the dividing
means 318. The adjustment in the transmission time interval/size
adjusting means 322 is set under control of parameter management
means 324 for managing a parameter that specifies, for example, the
transmission time interval. Further, the allocation means 316
include special signal generation means 326 for generating a
special signal (signal having only an Iub header) to be transmitted
to a mobile terminal in the case where a transmission block (TB) to
be transmitted to the mobile terminal does not exist.
[0030] The control signal processing means 310 include processing
means 328 for receiving an output signal of the combining means 314
via the switching means 306 and performing, for example, analysis
and determining of the control signal. In addition, the processing
means 328 may be used for generating a control signal transmitted
to the mobile terminal. The control signal processing means 310
include first determination means 330 for determining whether to
vary the transfer rate of the control channel according to need
(for example, in accordance with the kind and/or amount of data of
a signal to be transmitted). Preferably, the control signal
processing means 310 further include second determination means 332
for determining whether there are unused communication resources
(transmission bands) in a certain period based on the transfer rate
(currently) set to the control channel and the amount of data of a
signal to be actually transmitted via the control channel. That is,
it is also possible to consider the decision result of the second
determination means 332 when determining whether to vary the
transfer rate in the first determination means 330. The decision
result in the second determination means 332 is also given to
allocation means 316 (the parameter management means 324).
[0031] The transmission band management means 312 control
allocation and releasing of transmission bands for control channels
of mobile terminals that are used in the mobile communication
system based on the transmission bands (or the remaining
transmission bands) of the control channels currently being used.
In addition, the transmission band management means 312 serve a
predetermined notice to switching equipment and/or wireless base
stations in accordance with an increase/decrease of the unused
bands.
[0032] Referring to FIGS. 4, 5 and 6, a description is given of an
operation of the communication resource management device 300. FIG.
4 is a schematic diagram showing a breakdown of transmission bands
in the mobile communication system. Similar to FIG. 1, among the
available transmission bands in the entire system, a part thereof
is used for a control channel 402, another part thereof is used for
a communication channel 404, and the remaining part thereof is an
unused band 406. However, in this embodiment, even if the transfer
rate of the control channel for a certain mobile terminal is
varied, unless the number (N) of mobile terminals that perform
communications by using control channels is varied, the amount of
the transmission band 402 occupied by the control channels is
maintained constant among the available transmission bands in the
entire system. The transmission bands maintained constant are
expressed by N.times.Tw, where N is the number of mobile terminals
that perform communications by using control channels, and Tw is
the lowest transfer rate set and guaranteed in the mobile
communication system in a case where each mobile terminal performs
communications by using a control channel. N and Tw are used for
the same meanings as described with reference to FIG. 1. Thus, in a
case where each mobile terminal performs communications via its own
control channel, as in conventional cases, each mobile terminal
uses a band of Tw.
[0033] Meanwhile, in each control channel in uplinks and downlinks,
data equal to or less than a predetermined data size (TFS) are
transferred at predetermined transmission time intervals. In this
case, each control channel does not necessarily transmit data at
all of the predetermined transmission time intervals. There may be
a period during which data to be transmitted as a control signal do
not exist, that is, there is an unused communication resource that
is not being used for data transmission.
[0034] In this embodiment, such an unused communication resource is
found out and allocated to a control channel related to another
mobile terminal, thereby increasing the transfer rate of the
communication channel. Accordingly, it becomes possible to
correspond to the demand for high-speed control channels, and in
addition, those communication resources the use of which is not
determined are used for other control channels. Hence,
communication resources can be effectively used. Further, since all
the transmission bands 402 for control channels are maintained
constant among the available transfer channels in the entire
system, it is possible to avoid reducing the transmission bands 404
for communication channels and the remaining transmission bands
406. Accordingly, it is possible to eliminate various problems
caused by reducing the remaining transmission bands 406.
[0035] FIG. 5 shows how transmission blocks 502 (1-1, 1-2, . . . ,
1-6, 2-1, . . . , 4-4), which should be transmitted via
corresponding four control channels CH1 through CH4 are transferred
with respect to a time axis 504. FIG. 5 shows signals in cases (A)
and (B) where the radio network controller (RNC) 204 transmits, to
the wireless base station 206 (and the mobile terminal 208), the
contents of a signal (transmission blocks) generated by the RNC 204
or received from the higher level switching equipment 201. (A)
shows the case where transmission is performed to each mobile
terminal within the transfer rate guaranteed in the system. (B)
shows the case where the transfer rate of a control channel 1 is
increased, but the transfer rates of the other control channels are
maintained as is.
[0036] First, transmission blocks to be transmitted in each control
channel are accumulated (buffered) in the radio network controller
204. As for the control channel 1 (CH1), transmission blocks 1-1
through 1-4 are consecutively received or created, and then
transmission blocks 1-5 through 1-6 are received and accumulated in
preparation for transmission. As for the control channel 2 (CH2),
transmission blocks 2-1, 2-2 and 2-3 are intermittently received,
and each of them are accumulated in preparation for transmission.
As for the control channel 3 (CH3) and the control channel 4 (CH4),
similarly, transmission blocks 3-1 through 3-4 and 4-1 through 4-4
are received and accumulated, respectively. It should be noted
that, for simplicity, the timings for buffering transmission blocks
are illustrated as if they are the same as the timings for
transmitting the transmission blocks. However, actually, each
transmission block is transmitted after a predetermined time period
elapses since being buffered.
[0037] First, in the case of (A), it is possible to transfer a
signal in each control channel with the use of the minimum band Tw
that is guaranteed in the system. As shown in FIG. 5, if there are
data, transmission blocks of each control channel may be
transmitted at intervals of 40 ms at latest. In this regard, a
technique according to an embodiment of the present invention and
the conventional technique (FIG. 1) offer similar results.
[0038] Next, a description is given of the case where the transfer
rate of the control channel (CH1) is increased. Determination of
whether to increase the transfer rate of the control channel 1 may
be based on, for example, whether the data amount (traffic volume)
to be transmitted via the control channel 1 exceeds a predetermined
value. The transfer rate of the control channel 1 may be increased
in the case where a predetermined control step is started or the
case where a predetermined message is transmitted, such as when a
call is established or released. In any case, it is preferable to
increase the transfer rate in the case where the number of control
steps performed via the control channel with respect to a mobile
station is increased or the amount of control signals transferred
is increased. The determination is made by the first determination
means 330 of the control signal processing means 310, and is
communicated to the parameter management means 324.
[0039] Preferably, it is further determined in the second
determination means 332 whether there is a communication resource
that will be unused in the future in the control channels other
than the control channel 1. It is possible to find a communication
resource that will be unused based on the transfer rate currently
set to each control channel and the amount of data of transmission
blocks accumulated in each control channel for actual transmission.
For example, assuming fixed terms T1, T2, T3 and T4, each having a
time length of 40 ms, transmission of the transmission block 2-1,
which is transferred via the control channel 2, is completed during
the term T1 (the data size thereof is that much). Hence,
communication resources reserved for the control channels 2, such
as blocks 506 indicated by dotted lines, will be unused during the
terms T2 and T3. Similarly, as for the control channels 3 and 4, it
turns out that communication resources will be unused during the
terms T2 and T3. It is not essential that the fixed term assumed
for finding unused communication resources matches the transmission
interval in the case of the guaranteed minimum transfer rate, such
as 40 ms, and another fixed term may be assumed as well.
[0040] By allocating, to the control channel 1, the communication
resources for the control channel 2 and the control channel 3 found
to be unused in the aforementioned manner, signal transfer as shown
in (B) is performed. That is, in the Term T1, transmission blocks
are transmitted at intervals of 40 ms in the control channel 1. In
the terms T2 and T3, transmission blocks are transmitted at
intervals of 10 ms in the control channel 1. Transmission of up
through the transmission block 1-6 is completed within the term T3.
Thereby, compared to the case of (A), it is possible to complete
transmission in the control channel 1 within a half period.
[0041] Preferably, in the communication resource management device
300, a positive decision result (indicating necessity of
modification and that there will be unused resources in the future)
of the first determination means 330 and the second determination
means 332 is communicated to the allocation means 316, and what to
transmit at what timing is set. For example, as for the control
channel 1, transmission blocks are transmitted at intervals of 40
ms in the term T1. In the term T2, transmission blocks are not
transmitted at intervals of 40 ms, but the transmission blocks 1-2,
1-3 and 1-4 are transferred at intervals of 10 ms with the use of
communication resources for the control channels 2 and 3. Also in
the term T3, the transmission blocks 1-5 and 1-6 are transferred at
intervals of 10 ms. In order to realize such transfer, various
parameters are adjusted. The parameter management means 324 send
instructions to the transmission time interval/size adjusting means
322 such that the minimum transfer rate guaranteed in the system is
realized in the term T1 and a higher transfer rate is realized in
the terms T2 and T3. In accordance with the instructions, the
transmission time interval/size adjusting means 322 adjust the
transmission time intervals or data size.
[0042] The set items such as transmission time interval TTI and the
transmission data size TFS, which are varied by the control signal
processing means 310 and the allocation means 316, are communicated
to a corresponding wireless base station and a wireless base
station and a mobile terminal that are related to a control channel
to be varied. Then, it becomes possible for the radio network
controller to perform communications via a control channel having a
newly set transfer rate. It should be noted that, in this case, the
transmission band management means 312 need not specifically manage
allocation of communication resources in each control channel
between a mobile terminal and a wireless base station. As mentioned
above, the transmission band management means 312 control
allocation and releasing of communication resources for control
channels with respect to mobile terminals that are used in the
mobile communication system. Hence, the transmission band
management means 312 have only to recognize how much unused bands
are left in the entire system. Different from conventional
techniques, in this embodiment, if the number (N) of mobile
terminals performing communications with the use of control
channels is not changed, the transmission bands 402 (=N.times.Tw)
for control channels used in the entire system are not changed.
Thus, the unused bands 406 are not changed as well. The control
signal processing means 310 and the allocation means 316 can
determine how to allocate transmission bands in the transmission
bands 402 for control channels, without using the transmission band
management means 312. Further, the radio network controller may
unilaterally transmit varied set items to a mobile terminal before
starting variation of a wireless base station, and may vary the
transfer rate in a control channel without transmitting a signal to
and/or receiving a signal from the mobile terminal.
[0043] In the example shown in FIG. 5, the description has been
given of the rate in which transmission is made at intervals of 40
ms and the rate in which transmission is made at intervals of 10
ms. However, the number of kinds of transfer rate may be increased.
For example, options for performing transmission at intervals of 10
ms, 20 ms, 30 ms and 40 ms may be provided and suitably
selected.
[0044] The transmission time interval, such as 10 ms and 40, ms may
be associated with a delay time until a signal is buffered and
transmitted, i.e., quality of service (QoS). For example, a signal
received immediately after the transmission cycle of 10 ms is
buffered for approximately 10 ms and transmitted at the next
transmission timing. Thus, the delay time of a signal is different
between the case where the transmission time interval is 10 ms and
the case where the transmission time interval is 40 ms, and the QoS
is also different between these cases. Hence, it is advantageous to
divide the QoS realized in the system into two or more classes in
advance (for example, the transmission time interval TTI=40 ms may
represent a first class QoS1, and the transmission time interval
TTI=10 ms may represent a second class QoS2), to select an
appropriate class according to need, and to adjust the transfer
rate in a control channel, thereby managing allocation of frequency
bands. For example, the QoS may also be used in an operation of a
management timer in an ARQ (Automatic Repeat Request), and may be
used for signal processing other than transmission band
allocation.
[0045] Meanwhile, even with the conventional technique as described
with reference to the right side of FIG. 1, it is possible to
increase the rate in the control channel 1 as shown in (B) of FIG.
5. However, in such a case, the unused bands will be reduced in
return for increasing the rate in the control channel. It should be
noted that, according to an embodiment of the present invention,
under the condition that unused communication resources in control
channels are found, it becomes possible to increase the rate in any
of the control channels without reducing the unused bands.
[0046] On the other hand, when the decision result in the second
determination means 332 of the communication resource management
device 300 is negative, it implies that there are no such
communication resources that are not going to be used during a
predetermine term such as T2 and T3 in the communication resources
for the control channels other than the control channel 1. It is
desirable that all control channels guarantee that communications
may be performed at a predetermined communication rate or a higher
communication rate. It is undesirable for the communication rate of
another control channel having data to be transmitted to be reduced
for increasing the communication rate of a certain control channel.
Accordingly, as shown in FIG. 6, in the case where each control
channel includes a large amount of data to be transmitted and is
congested, even if the decision result in the first determination
means 330 indicates necessity of variation, the second
determination means 332 send notification that there will be no
resources available. Thus, the allocation means 316 do not approve
variation of the transfer rate, and each control channel transmits
its own transmission blocks at the minimum rate guaranteed in the
system. In the example shown in FIG. 6, each of the control
channels 1 through 4 transmits its own transmission blocks at
intervals of 40 ms.
[0047] In the above description, the transmission transfer interval
(TTI) is adjusted so as to vary the transfer rate of a control
channel. However, the data size (TFS) of data to be transmitted at
a time as well as the transmission time interval may be varied so
as to vary the transfer rate.
[0048] FIG. 7 shows conditions where transfer rates are varied by
varying the transmission time intervals or the data size. Each
timing chart shows a condition where transmission blocks TB1
through TB4, each having a predetermined data size, are transferred
from a transmitting node to a receiving node. In the timing chart
indicated by (A), one transmission block is transferred at
transmission time intervals of a first term D1. In the timing chart
indicated by (B), one transmission block is transferred at
transmission time intervals of a second term D2, which is a half of
the first term D1. In this manner, a transfer rate twice the
transfer rate in the case indicated by (A) is achieved. In the
timing chart indicated by (C), two transmission blocks are
transferred at transmission time intervals of the first term D1.
Also in this manner, it is possible to achieve a transfer rate
twice the transfer rate in the case indicated by (A). Further,
though not shown in the figure, it is also possible to further
increase or decrease the transfer rate by adjusting both
transmission time interval and data size.
[0049] As mentioned above, according to this embodiment, it is
possible to effectively use communication resources by varying the
transfer rate in a control channel related to a mobile terminal in
accordance with a communication condition. Additionally, according
to this embodiment, it is possible to vary the transfer rate in a
control channel related to each mobile terminal without varying the
sum of transmission bands for control channels.
[0050] In the above description, the transfer rate of only one
control channel is increased. However, the transfer rates of a
greater number of control channels may be increased. Further, a
particular description has not been given of variation in the
wireless zone between a wireless base station and a mobile terminal
due to variation in a transfer rate (e.g., twice). However, in the
case where, for example, wireless communications are being
performed with the use of a spread code A (spread rate x), it is
possible to vary a transfer rate in the wireless zone by newly
assigning a spread code B (spread rate x).
Second Embodiment
[0051] Data transfer from a transmitting node to a receiving node
is performed such that a signal of a predetermined data size, such
as 1 block or 2 blocks, is transferred at predetermined
transmission time intervals (TTI) such as 10 ms or 40 ms.
Generally, the format of a signal transmitted from and received by
a radio network controller (RNC) is as shown in FIG. 8 and includes
a header 802 and a subsequent payload 804. The payload 804 includes
transmission blocks 1, 2, 3, . . . to be transferred. The header
802 includes a transport format indicator (TFI), which indicates
the number or amount of the transmission blocks (TB) following the
header. Although an actual TFI is a value related to the data
amount of transmission blocks, the actual TFI is not always a
numeric value directly representing the number of transmission
blocks. However, for convenience of explanation, it is assumed that
a TFI directly represents the number of transmission blocks. For
example, when TFI=3, then 3 transmission blocks (TB1, TB2, TB3) are
included in a payload as shown in FIG. 8. In addition, the data
amount of a transmission block is also determined in advance, which
may be, for example, 40 bytes/packet.
[0052] When transferring transmission blocks, of course the
transmission blocks are transferred at predetermined transmission
time intervals by using a signal format as mentioned above.
However, conventionally, even when there is no transmission block
to be transmitted, certain signals have been transmitted at
transmission time intervals. For example, when establishing a call,
relatively many signals are transferred. However, in a stabilized
period after a connection is established, the number of
transmission blocks to be transferred by using a control channel is
significantly decreased. In this case, the signal may not be
transferred at transmission cycles defined by a TTI. However, in
such a case, there is concern that the transmitting node and the
receiving node may not be synchronized. Thus, even if there is no
transmission block to be transmitted, a special signal (or NoDATA
signal), such as a signal having only the header 802, is
transferred at transmission cycles. In the case where a wireless
base station has not received any signal during a predetermined
time frame, the wireless base station can maintain synchronization
between nodes by transmitting a time adjustment (TA) signal. The
TFI included in NoDATA indicates that the number of transmission
blocks is 0 (TFI=0).
[0053] It is contemplated to apply such a technique to the
above-mentioned first embodiment. For example, it is assumed that a
first mode where transmission is performed at the minimum transfer
rate of 40 ms and a second mode where transmission is performed at
the maximum transfer rate of 10 ms are prepared. In this case, in
the first mode, transmission blocks TB or special signals are
transmitted at intervals of 40 ms. In the second mode, transmission
blocks TB or special signals are transmitted at intervals of 10
ms.
[0054] However, the intended purpose of the second mode is high
speed transfer of transmission blocks. Thus, when there is no
transmission block to be transmitted, it is impractical to perform
high speed transfer by increasing traffic by using frequency
resources for another control channel.
[0055] Hence, in this embodiment, in addition to a transmission
time interval for transferring transmission blocks TB, another
transmission time interval is prepared for transferring special
signals (NoDATA signals), and the latter is set longer than the
former. In the above-mentioned example, transmission blocks are
transmitted at intervals of 10 ms in the second mode. However, when
there is no transmission block, special signals (NoDATA signals)
can be transmitted at intervals of 40 ms. Additionally, in the
first mode, transmission blocks and special signals are transmitted
at intervals of 40 ms.
[0056] FIG. 9 is a timing chart showing signal transfer in a
downlink according to the second embodiment. FIG. 9 shows a
condition (A) where a wireless network controller (RNC) (more
properly, the communication resource management device 300)
receives control signals (transmission blocks) 1-1 and 1-2 from the
higher switching equipment 201, and a condition (B) where the radio
network controller transmits the control signals 1-1 and 1-2 to a
wireless base station under the radio network controller. For
convenience of explanation, the communication resource management
device 300 is set to operate in the second mode, which is the high
speed mode. Thus, as indicated by (B), the transmission blocks 1-1
and 1-2 to be transmitted are transmitted to the wireless base
station at transmission time intervals of 10 ms. Since there are no
more transmission blocks, after the transmission blocks 1-1 and 1-2
are transmitted, special signals S are transmitted at intervals of
40 ms. The special signals S are created by special signal
generation means 336 under management of the parameter management
means 324 in the allocation means 316, and are supplied to the
transmission time interval/size adjusting means 322. It should be
noted that the dotted lines shown in (B) represent special signals
created and transmitted when TTI for the special signals S are not
prepared.
[0057] In the example shown in the figure, the special signals S
are transmitted at intervals of 40 ms from a predetermined time
point that is set for the special signals S. However, this is not
necessary for the present invention, and transmission may be made
from an arbitrary time point after the transmission block 1-2 is
transmitted. For example, transmission may be made at intervals of
40 ms after the last transmission block (1-2) is transmitted.
[0058] FIG. 10 is a timing diagram showing signal transfer in
uplinks according to the second embodiment. FIG. 10 shows the case
(B) where the communication resource management device 300 receives
control signals (transmission blocks) 1-1 and 1-2 from the mobile
terminal 208 and the wireless base station and the case (A) where
these are transmitted to the switching equipment 201. Also in this
case, the communication resource management device 300 is set to
operate in the above-mentioned second mode, which is the high-speed
mode. Accordingly, as shown in (A), the received transmission
blocks 1-1 and 1-2 are transmitted to higher switching equipment at
intervals of 10 ms. Although there are no more transmission blocks,
the communication resource management device 300 receives special
signals S at intervals of 40 ms even after receiving the
transmission block 1-2. Further, the dotted lines shown in (B)
represent special signals to be received when TTI for the special
signals S are not prepared. In the example shown in the figure, the
special signals S are transmitted at intervals of 40 ms from the
time point set for the special signals S. However, as described
with reference to FIG. 9, transmission may be made from another
time point.
[0059] According to this embodiment, in addition to the effect of
the first embodiment, which increases the speed of the control
channel, there is no need to frequently transfer special signals
such as NoDATA. Hence, it is possible to use communication
resources related to a decrease in traffic for other
communications. Thus, it is possible to more effectively use
communication resources.
[0060] The present invention is not limited to the specifically
disclosed embodiments, and variations and modifications may be made
without departing from the scope of the present invention.
[0061] The present application is based on Japanese priority
application No. 2002-246655 filed on Aug. 15, 2002, the entire
contents of which are hereby incorporated herein by reference.
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